Small diameter arterial prostheses fail at unacceptably high rates. This is thought to be due in part to an incapacity of human endothelial cells (ECs) to spontaneously fully line (or heal) the prosthesis and thereby decrease surface thrombogenicity. Graft failure also occurs due to the uncontrolled proliferation or hyperplasia of vascular wall cells (smooth muscle and fibroblasts) which obstructs the graft lumen leading to thrombosis. The lack of EC healing probably contributes to this as well. Thus, an optimally healed graft can be defined as one with confluent non- thrombogenic endothelium in which hyperplasia is controlled. The capability of this laboratory to culture adult human vascular ECs and to examine their extracellular matrix (ECM) biology will be used to prove the hypothesis that the lack of optimal healing in human implants is not due to an inherent limitation of the ECs themselves, but to the improper and potentially hostile environment in which they are asked to grow. Cultured adult human EC from venous, arterial and microvascular sources, as well as from young and old donors with and without peripheral vascular disease, will be characterized as to their ability to heal a prosthetic surface. We will measure their attachment to, growth and migration on, and adhesion (resistance to shear stress) to a series of test surfaces, including relevant biomaterials, which will be coated with specific macromolecules (types I, III, and IV collagen, fibronectin, laminin, proteoglycans and glycosaminoglycans) that are associated with ECM. Using biosynthetic, immunological, and molecular biological approaches, we will also examine the effect of substrate on the synthesis of ECM components, and of growth factors, some of which are known to be mitogenic for vascular wall cells. The influence of physical parameters such as compliance of the substrate and shear stress due to flow will also be studied. This study of EC healing ability, and of the factors which influence it, will lead to the identification of a prosthetic environment, after implantation, is more conductive to the above defined optimal healing, and thereby yield the desired improvement in bypass graft patency.